The goals of this project are to investigate the molecular pathogenesis of diffuse aggressive malignant lymphomas by characterizing genes that contribute to their induciton and progression. These studies will focus on continued efforts to identify new cellular proteins whose alterations play a fundamental role in lymphoid cancers. For the studies proposed in the first specific aim, chromosomal translocations will serve as genetic markers for novel cellular oncogenes at the breakpoints. Using molecular biological techniques, translocation breakpoints will be assessed for their potential involvement of chromosomal loci that activate cellular oncogenes by transcriptional mechanisms (e.g. the immunoglobulin and T cell receptor genes) or by protein fusions (r.g. the E2, HRX, or NPM genes). In the second specific aim, the molecular pathogenesis of aggressive T cell lymphomas will be addressed employing a novel transgenic model. The latency for transgene-associated lymphomas will be shortened by neonatal injection of Moloney Leukemia Virus (MLV). Genomic DNA from accelerated tumors will be used to characterize the sites of MLV integration by molecular cloning. Cellular genes that flank the sites of MLV integration will be identified and characterized for their potential relationships to known proto-oncogenes. Novel genes will be fully characterized by cDNA cloning and sequencing. These studies will identify genes capable of accelerating T cell lymphomagenesis in vivo and provide reagents for additional biochemical studies and assessment of their roles in human lymphomas. The third specific aim addresses the biochemical properties of newly discovered oncoproteins which will be characterized using several different experimental approaches. These will address the transcriptional regulatory properties of Ly11, the original member of a subclass of basic helix-loop-helix proteins that is involved in a significant fraction of lymphoblastic lymphomas. DNA-binding protein complexes containing Ly11 will be characterized in cultured cell lines using EMSA techniques and monospecific antibodies. The transcriptional properties of Ly11-containing heterodimers will be assessed on synthetic reporter genes containing the Ly11 consensus site in transiently transfected cells. These and other assays will be employed for a structure/function analysis of Ly11 and its role in transcriptional control of physiologic events in lymphoid cells. Genes whose expression are subordinate to Ly11 will be investigated by chromatin enrichment and/or subtractive cloning techniques. infractions of Lyl1 with heterologous cellular proteins will be characterized using yeast genetic and biochemical approaches. The studies in this project will enhance our understanding of the molecular events governing lymphocyte differentiation and growth control and the mechanisms for their disruption in lymphoid malignancies.